| 摘要 |
PURPOSE:To keep an object image distance always constant, by constituting a zoom lens system consisting of 2 moving lens groups, of a pre-group and a post- group having a positive focal length and a negative focal length, respectively, in order from the side of an original. CONSTITUTION:A zoom lens system consists of 2 lens groups moving along an optical axis going toward the drum side from the original side, and a pre-group A and a post-group B from the original side are of a telephoto type having a positive focal length and a negative focal length, respectively. Even if the zoom lens system is moved to magnification 9c, 9c' from equal magnification 9a, when the pre-group A having a positive focal length is compared with the previous pre-group having a negative focal length, the extent of moving in the semi-speed mirror direction is small, therefore, a moving area of the semi-speed mirror is magnified as a matter of course. |
